The present invention relates to a vibrating cutting tool adapted to impart vibrations effective for cutting to a rotary cutter such as a drill or a mill.
FIG. 19 shows how the work A made of a metallic material is machined with the edge B of a cutter. Let us suppose that the cutter is moving to the lefthand side of the figure. Letter C designates the chip produced by machining.
Viewing in a minute scale, the cutter edge B proceeds in the direction of arrow not smoothly but discontinuously in a stop-and-go manner to alternately compress and shear the work. The chip C thus produced is composed of a plurality of blocks C' piled one upon another.
The vibration produced by such stop-and-go motion of the cutter edge during cutting is called self-induced vibration. Ordinarily, it has an extremely minute amplitude but such a cutting can be regarded as vibration cutting in a broad sense. If its amplitude exceeds a certain point, however, such vibration becomes chattering.
FIG. 21A shows a waveform during a conventional cutting state as described above. It is very irregular. Heat tends to build up at portions where waves are small and the work tend to have scratches formed at portions where they are large. This will worsen the surface roughness.
There is also known another type of vibrating cutting tool in which the cutter is forced to vibrate so as to cut the work by giving uniform vibrations to the cutter as shown in FIG. 21B. Such a cutting tool has excellent cutting characteristics.
But, as a vibration generator, an electrostriction or magneto-striction type vibrator excited by an oscillator have been used. Other types such as an electromagnetic type, electro-hydraulic type and mechanical-hydraulic type are also known. Such conventional means for vibrating a cutter need a complicated circuit or a large-sized, complicated and costly device such as a hydraulic cylinder.